That's a bit negative; it's the source for the WebGL implementation; rather than wait X amount of time till they can do the 'proper' release; the source is available to read, how can you be mad at that?

This is something Microsoft would never have done in the past, and I think we should applaud the efforts that are being made.

Lastly; they are doing this to improve interoperability; give them some credit for the effort.